computer world

  Security in distributed Environment  Securities strategies must be as drivers and customized as are indivisible computing environment. Many e large organisation have a vast number of computers in use in many different areas.  To computing functions typically report to several different part of the organisation rather than to a centralized system or security group. Yet most security function will attempts to operate as a centralized control and support function.  The security function has been centralized focus because-  The client for user areas do not have the expertise them selves.  The Client or user areas do not fully accept or understand security requirements.  The Client or user areas cannot provides the necessary level of Reliability in terms of process and counter balances.  The system supports functions are largely centralized.  Although these argument may be legitimate they can no longer be used to justify maintaining centralized system security in a business environment in

  Swapping in operating system Swapping  Swapping is a memory management scheme in which a any process is temporary swapped from main memory to secondary memory. Main memory can be made available for other process it is use to improve main memory utilization. A place in the secondary memory where the swapped out process is stored this space is known as swap space.   Swapping policy is used for priority based scheduling algorithm if a higher priority process arrive and want service, the memory manager can Swap out the lower priority process and then load and execute the higher priority process. When a higher priority process finishes the lower priority process can be swiped in a continuous this type of swapping is sometime called roll out roll in. Advantages of swapping   It help the CPU to manage multiple process within a single memory. It improves the main memory utilization. Disadvantages  of swapping  If the swapping algorithm is not good, the composite can increase the number of pa

  Single partition allocation, Multiple-partition allocation and Fixed Equal-size partitions in operating system Single partition allocation In this scheme operating system is residing in law memory and user process are executing in higher memory. Advantages It is simple  It is easy to understand and use Disadvantages User job is limited to the size of available memory. It leads to poor Utilization of processor and memory. Multiple-partition allocation  It is the simplest method for allocating  memory is divided memory into several fixed size partitions. Fixed Equal-size partitions It divides the main memory Into equal number of fixed sized partitions, operating system occupies some fixed portion and remaining portion of main memory is available for user processes. Advantages It supports multi programming. A process whose size is less then or equal to the partitions size can be loaded into any available partition. Disadvantages If a program is big to fit into a partition use overlay te

 First fit  Allocate the first hole that is large enough. In other word we can say that In the first fit the partition is allocated which is the first block from the top of the main memory. So it scan memory from the beginning and choose the first block that is large enough. Advantage of first fit memory allocation It is fast in processing It is very fast in execution Disadvantage of first fit memory allocation It west lot of memory. Best fit Allocate the smallest hole that is big enough. In other words we can say that in the best fit, allocate the process to the partition which is the smallest sufficient partition among the free available. Advantage of best fit allocation   The operating system allocates the job minimum possible space in the memory making, memory management very efficient. To save memory from getting wasted, it is the best method. Disadvantage of best fit allocation It is a slow process  It takes lot of time to complete the work   First fit, Best fit and Worst fit in

  Deadlock in operating system-computer world Deadlock :  In a multi-programming environment, many process may complete for a minute number of resources. A process make a request for a resource and if the resource is not available at that time, the process enter In a waiting state. A waiting state process is never again-able to change state because the resource it has requested is held by other waiting process. This situation is called deadlock. So we can say that a process is said to be deadlock when it is waiting for an event or resources which will never occurs.   so we can say that in this situation none of the process gets executed  since the resource it needs, is held by some other process which is also waits for some other resource to be released.  Let's assume that there are three process P1, P2, p3 and three different resources R1, R2 and R3. R1 is assigned to p1, R2 is assigned to P2 and R3 is assigned to P3.   After sometime P1 demands for R1 which is being used by  P2.

Memory management in operating system-computer world Memory management :   The function of operating system which manages the memory of a computer for the processing of the program this management is known as memory management. There are several programs that consist in memory, so it became to move programs and data around the memory of a memory management system is the collection of hardware and software procedures for the Managing various program consisting in the memory. Memory management play an important role in operating system to improve the speed speed of the computer system.   Memory management determines how  memory is allocated between the processes,  deciding which gets memory, when they receive it and how much they are allowed. When memory is allocated it determines which memory location will be assigned. Main memory refers to a physical memory that is the internal memory of the computer. Main memory is also known as RAM. The computer is able to change only data that is in

 Preemptive and non preemptive  Preemptive   In preemptive Scheduling algorithm, the the running process is interested by the higher priority process. When a currently running  process finish execution, the priority of the ready state process is checked against that of the running process. If the priority of the ready process is higher, it is allocated to the CPU. A Scheduling discipline is primitive, if the CPU is taken away from the process after being allocated.  Cost of the preemptive scheduling is higher then non preemptive scheduling. Higher priority jobs are processed before the lower priority jobs.  Non preemptive In non preemptive Scheduling, the CPU has been allocated to a process, the process keeps the CPU until it release the CPU either by switching to the waiting state. This scheduling method is used by Microsoft Windows 3.x, window 95 introduced preemptive scheduling. A scheduling discipline is non preemptive, if the process has been given the CPU, the CPU cannot taken aw

  Multilevel queue Scheduling in operating system Multilevel queue Scheduling  Multilevel queue Scheduling algorithms has been created for situation in which processes are easily classified into different groups. A common division is made between foreground processes and background processes. In this scheduling algorithm, process in the ready queue can be divided into different classes where each class has its own scheduling needs. In other word we can say that a multilevel queue scheduling algorithm partition the ready queue into several separate queue. The process are permanently assigned to one queue, generally based on some property of the process, such as memory size, process priority, or process type. Each queue it's own scheduling algorithm. For example, a common process division is a foreground process and background process. The foreground queue is scheduled by an RR algorithm, while the background queue is scheduled by an FCFS algorithm. The process scheduler is alternate